In general, a method to get fingerprint information among biometric information about the human includes an indirect method using a picture input device such as a scanner or a camera to capture a part of the fingerprint of a finger which is imprinted on a paper and an optical method and a non-optical method using an electric field.
Among others, the optical method is the most efficient and universal method. A device to get the fingerprint with an optical method is typically called an optical fingerprint input device.
Such an optical fingerprint input device diffuses light emitted from a light source, allows a fingerprint picked by a prism to be imaged through a lens, and converts a shape of the fingerprint into electrical signals using a sensor. The converted electrical signal is subjected to an image processing to acquire a fingerprint image.
In the optical fingerprint input device, a residual fingerprint is generated by sebum and dirt in accordance with the contact of the fingerprint and a variety of background noises is induced in the course of acquiring the fingerprint image. The residual fingerprint and the background noise have a close relationship with respect to a recognition rate of the fingerprint and security in a fingerprint recognition technology, and thus various researches are in progress in order to remove them.